Messages in this thread | | | Date | Thu, 29 Jul 2010 00:56:17 +0900 | From | Minchan Kim <> | Subject | Re: [PATCH] Tight check of pfn_valid on sparsemem - v4 |
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On Wed, Jul 28, 2010 at 10:14:51AM -0500, Christoph Lameter wrote: > On Wed, 28 Jul 2010, Minchan Kim wrote: > > > static inline int memmap_valid(unsigned long pfn) > > { > > struct page *page = pfn_to_page(pfn); > > struct page *__pg = virt_to_page(page); > > Does that work both for vmemmap and real mmapping?
When Kame suggested this idea, he doesn't consider vmemmap model. (He prevent this featur's enabling by config !SPARSEMEM_VMEMMAP)
config SPARSEMEM_HAS_HOLE bool "allow holes in sparsemem's memmap" depends on ARM && SPARSEMEM && !SPARSEMEM_VMEMMAP default n
When I change it with ARCH_HAS_HOLES_MEMORYMODEL, it was my mistake. I can change it with ARCH_HAS_HOLES_MEMORYMODEL && !SPARSE_VMEMMAP.
I wonder whether we supports VMEMMAP. That's because hole problem of sparsemem is specific on ARM. ARM forks uses it for saving memory space but VMEMMAP does use more memory. I think it's irony.
> > > return page_private(__pg) == MAGIC_MEMMAP && PageReserved(__pg); > > } > > Problem is that pages may be allocated for the mmap from a variety of > places. The pages in mmap_init_zone() and allocated during boot may have > PageReserved set whereas the page allocated via vmemmap_alloc_block() have > PageReserved cleared since they came from the page allocator. > > You need to have consistent use of PageReserved in page structs for the > mmap in order to do this properly.
Yes if we supports both model.
> > Simplest scheme would be to clear PageReserved() in all page struct > associated with valid pages and clear those for page structs that do not > refer to valid pages.
I can't understand your words. Clear PG_resereved in valid pages and invalid pages both?
I guess your code look like that clear PG_revered on valid memmap but set PG_reserved on invalid memmap. Right?
invalid memmap pages will be freed by free_memmap and will be used on any place. How do we make sure it has PG_reserved?
Maybe I don't understand your point.
> > Then > > mmap_valid = !PageReserved(xxx(pfn_to_page(pfn))
-- Kind regards, Minchan Kim
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